Process for the preparation of 2,5-dihydrofuran

ABSTRACT

A process for the hydrogenation of butadienepolyperoxide in a suitable solvent, e.g., tetrahydrofuran, at temperatures of 75°-110° C. and pressure above 2000 psia by contacting the butadienepolyperoxide and hydrogen in the presence of metallic silver. The process produces 1-butene-3,4-diol and 2-butene-1,4-diol.

This is a division of application Ser. No. 013,236, filed Feb. 21, 1979.

TECHNICAL FIELD

This invention relates to the preparation of diols frombutadienepolyperoxide. More specifically, this invention relates to thepreparation of butenediols from the hydrogenation ofbutadienepolyperoxide over a silver catalyst.

BACKGROUND ART

U.S. Pat. No. 2,879,306 discloses the hydrogenation ofbutadienepolyperoxide over palladium, nickel, rhodium, cobalt andplatinum. A second stage hydrogenation over copper chromite, molybdenumsulfide and nickel is also disclosed. The resulting product is a mixtureof 1,4-butanediol and 1,2-butanediol. The 1,2-butanediol is not usedcommercially and therefore is less valuable than the 1,4-butanediol.

Handy and Rothrock in J. American Chemical Society, 80, 5306 disclosethe hydrogenation of butadienepolyperoxide in a silver-lined reactorover palladium followed by hydrogenation over ruthenium. The productswere 2-hydroxybutanal, 1,2-butanediol and 1,4-butanediol.

British Pat. No. 1,018,661 discloses the hydrogenation of unsaturatedorganic hydroperoxides over modified palladium or platinum catalysts togive unsaturated alcohols. Modifiers disclosed include silver. Animprovement in the amount of hydroperoxides reduced is shown with themodified catalysts.

Japanese Pat. Nos. 096634 and 087126 disclose the hydrogenation ofbutadeneperoxide polymer over Raney nickel to give 1,2- and1,4-butanediol.

U.S. Pat. No. 4,002,692 discloses the hydrogenation of polymericbutadieneperoxide over a nickel catalyst to prepare 1,2- and1,4-butanediol.

The reduction of butadienepolyperoxide to butanediols in the prior artgives maximum yields of the desired 1,4-butanediol of about 50% with a20-30% yield of the commercially unattractive 1,2-butanediol. Thereduction is carried out using a catalyst which rapidly becomesinactivated by contact with the peroxide and must be regeneratedfrequently. The reduction is very exothermic and is usually donestepwise under successively more severe conditions until reduction iscomplete.

The preparation of 1,4-butanediol is important not only for uses assolvents and monomers for the preparation of polyesters but also for usein the preparation of tetrahydrofuran.

The preparation of 1,4-butanediol by condensation of formaldehyde andacetylene to 2-butyne-1,4-diol followed by reduction to 1,4-butanediolis another process well known in the art and is a process that ispracticed commercially. However, because of the escalating cost ofacetylene, this process may rapidly become uneconomical.

Also described in the art is the oxidation of butane or benzene tomaleic anhydride followed by reduction to butanediol or tetrahydrofuran.

DISCLOSURE OF THE INVENTION

Now a process has been found for the hydrogenation ofbutadienepolyperoxide to form butenediols.

Accordingly, the process of this invention is a process for thehydrogenation of butadienepolyperoxide which comprises hydrogenating a1-20% by weight mixture of butadienepolyperoxide in a solvent which isnot subject to hydrogenation in the presence of hydrogen and a catalystcomprising at least 0.1% by weight of metallic silver at a temperatureof from 75°-110° C. and a pressure of at least 2000 psia to form areaction product comprising 1-butene-3,4-diol and 2-butene-1,4-diol.

Hydrogenation of the 2-butene-1,4-diol yields 1,4-butanediol. Thus,2-butene-1,4-diol can be converted to 1,4-butanediol by hydrogenation at150°-200° C. using the same hydrogenation catalyst disclosed herein forthe hydrogenation of the polyperoxide. However, 2-butene-1,4-diol mayalso be hydrogenated to 1,4-butanediol in the presence of a Raney nickelcatalyst or other known hydrogenation catalysts according to proceduresknown in the art.

The 1-butene-3,4-diol can be converted to 2,5-dihydrofuran by treatmentwith a soluble mercury salt in a hydroxylic solvent as disclosed in theart, e.g., U.S. Pat. No. 3,812,158. 2,5-Dihydrofuran is useful in thepreparation of tetrahydrofuran.

Butadienepolyperoxide can be prepared by converting butadiene thereto byany suitable oxidation process wherein a substantial portion of thebutadiene is converted to the polyperoxide. Butadiene may be oxidized ina suitable solvent in the liquid phase in the presence of air or oxygento form butadienepolyperoxide. The oxidation can be conducted in anysuitable pressure reactor provided with means to thoroughly mix air oroxygen and the butadiene. Contact times for the oxidation are from0.1-25, preferably 1-5 hours. Said oxidation is conducted in thetemperature range of 35°-120° C. and at a partial pressure of oxygen ofat least 20 psi. An initiator is preferably used to start the oxidation.Suitable initiators are organic peroxides or other precursors of freeradicals such as azobisiosbutyronitrile. Oxidation promoters such asacetaldehyde, cobalt, linoleate and the like may be used.

The solvent for hydrogenating the butadienepolyperoxide is any solventfor butadienepolyperoxide that under the reaction conditions ofhydrogenation disclosed herein is not hydrogenated and which does notcause decomposition of the polyperoxide. Representative examples includetetrahydrofuran, ethyl acetate, methyl acetate, 50-50toluene-tetrahydrofuran, 50-50 benzene-tetrahydrofuran, similar estersand ethers and their combinations in the hydrocarbons. For economicreasons, the most suitable solvents are those which may also be used forthe preparation of the polyperoxide, and methyl acetate is preferred.

The concentration of butadienepolyperoxide in the solvent may be up to20% inclusive by weight. Concentrations of 1-20% by weight are generallyused. Preferably the concentration of butadienepolyperoxide is 2.5-10%by weight in the solvent. Concentrations lower than 1% by weight, whileoperable, are uneconomic while concentrations higher than 20% may bedangerous. The hydrogenation is very exothermic and if reactiontemperatures are allowed to rise above about 120° C., the polymer maydecompose violently.

Butadienepolyperoxide hydrogenation temperatures from 75°-110° C. aregenerally used, with a preference for temperatures between 90°-105° C.Temperatures below 75° C., while operable, are uneconomical due to theslow reaction. Temperatures above 110° C. result in substantially moredecomposition products thereby reducing the yield of diols.

The use of continuous flow equipment for the reaction is preferred andthe rate of butadienepolyperoxide injection is a function of theperoxide concentration, of the weight of catalyst in the reactor, of thereaction temperature and the hydrogen pressure. At the higherpermissible temperatures and pressures, the residence time in thereactor may be a few minutes while at the lower operable temperatures, aresidence time of several hours may be necessary.

The pressure may generally range rather broadly. Best yields of diolsare obtained at hydrogen pressures above 2000 psi. Pressures between2000-5000 psi H₂ are preferred. However, higher pressures may be used.

The catalyst may be supported or unsupported silver metal. Ifunsupported, it may be prepared by reducing silver oxide with hydrogenor other reducing agents or by leaching out an alloy composition such asAg-Zn with alkali to remove the Zn and leave a silver alloy skeletonwith a high surface area. Supported catalysts may be prepared byreducing silver salts impregnated on a support by heating under hydrogenor by treating with a chemical reducing agent such as sodiumborohydride. Suitable supports are silica, alumina, diatomaceous earth,carbon and titania. The most active silver catalysts are those preparedon high surface area supports.

The concentration of silver metal on the support may be 0.1% by weightor more. Generally, the silver metal concentration is from 0.1-10% byweight, preferably 1-10%. Supported catalysts are preferred becausegreater activity can be achieved per weight of silver present.Especially preferred are 1-10% Ag on high surface area silica gelcatalyst.

The process of the present invention negates the disadvantages of theaforementioned prior art and commercial processes currently employed forthe production of 1,4-butanediol. The subject process utilizes astarting material lower in cost than acetylene and formaldehyde(butadienepolyperoxide may be simply prepared by the oxidation ofbutadiene at 100° C. under low pressures). By reactingbutadienepolyperoxide under critical temperature and pressure conditionsin the presence of a silver catalyst which acts uniquely to allowcleavage of the --O--O-- bonds and not the --C═C-- bonds, the peroxidebonds are hydrogenolyzed without saturation of the carbon-to-carbonbonds to yield the unsaturated diols, 1-butene-3,4-diol and2-butene-1,4-diol.

After solvent removal, the 1-butene-3,4-diol being lower boiling isreadily separated from the 2-butene-1,4-diol. The 1-butene-3,4-diolseparated from the reaction mix may be readily converted in good yieldsto 2,5-dihydrofuran. By converting the 1-butene-3,4-diol to a usefulproduct (not possible with 1,2-butanediol) the yield of desirableproducts is increased. The 2,5-dihydrofuran may be hydrogenated directlyto tetrahydrofuran or to a mixture of tetrahydrofuran and1,4-butanediol. The 2-butene-1,4-diol remaining in the original reactionmixture is reacted further at temperatures of 150°-200° C. under apressure of at least 2000 psi using the starting Ag catalyst to form1,4-butanediol. If desired, the 2-butene-1,4-diol reaction product maybe separately reacted using a Raney nickel catalyst to form the1,4-butanediol. Thus, by utilizing the route of the present inventionfeaturing the formation of the unsaturated diols as intermediates, anoverall yield of over 75% of tetrahydrofuran plus 1,4-butanediol may beachieved. This high yield makes this process commercially advantageous.Another process advantage lies in the fact that the reduction ofbutadienepolyperoxide is very exothermic. By utilizing the processforming the unsaturated diols at lower reaction temperatures, as theintermediate step to the final formation of the desired end products(1,4-butanediol and tetrahydrofuran) and heat load is thereby splitmaking the process easier to control.

The hydrogenation of the 2-butene-1,4-diol may be under the sameconditions as indicated above for the butadienepolyperoxidehydrogenation except for the temperature which is in the range of150°-200° C. However, any method known in the prior art may be used tohydrogenate the 2-butene-1,4-diol. For example, hydrogenation may beaccomplished over a Raney nickel catalyst at from 50°-200° C. and from30-5000 psi of hydrogen. Other known hydrogenation catalysts may beused. Under many conditions some of the other products in the reactionproduct, e.g. 4-hydroxybutyraldehyde, hydroxymethylvinylketone and2-hydroxybutene-3-aldehyde, are also converted to diols during thehydrogenation.

The conversion of 1-butene-3,4-diol to 2,5-dihydrofuran by the processdisclosed in U.S. Pat. No. 3,812,158 involves contacting the1-butene-3,4-diol with soluble mercury salts such as H_(q) SO₄ in ahydroxylic solvent, e.g., water or butanol, which is neutral or acidicat a moderate temperature, e.g., 20°-110° C.

The conversion of 2,5-dihydrofuran to tetrahydrofuran is well known inthe art.

EXAMPLES

The following examples further illustrate the process of the presentinvention. All percentages in the examples are by weight unlessotherwise indicated.

Example 1

A Hastelloy C reactor of 5 ml volume was packed with 1.55 g of a 10% Agon silica gel in fibrous form. The catalyst was prepared by impregnatingthe fibers with an ammoniacal silver nitrate solution, washing withdilute ammonium hydroxide and then with water and finally drying theproduct at 200° C. The dry catalyst was heated in the reactor at 250° C.for 54 hours under 2500 psi H₂ to reduce it. A solution containing 6.2%by weight butadienepolyperoxide in tetrahydrofuran and 1.147% by weight1,6-hexanediol as a standard for gas chromatograph analysis was injectedat 6 ml/hr into the top of the reactor under 2850 psi H₂ pressure. Theinternal temperature of the catalyst bed at the start of injection wasadjusted to 97° C. by heating with a fluidized sand bath. Thebutadienepolyperoxide solution was allowed to trickle downward throughthe catalyst bed and withdrawn from the bottom of the reactor at thesame rate as it was injected. An exothermic reaction which raised theinternal temperature to 102° C., or 5° above the temperature of the sandbath, was noted. The effluent was assayed by gas chromatography,relating the amount of each product to the known quantity of1,6-hexanediol present. After seven reactor volumes had been added andwithdrawn, a steady state was reached. The yields of the variousproducts were:

48.24%--1-butene-3,4-diol

30.28%--2-butene-1,4-diol

2.64%--4-hydroxybutyraldehyde

1.49%--2-hydroxybuten-3-aldehyde and hydroxymethyl vinyl ketone

The products are over 99% unsaturated.

EXAMPLE 2

The apparatus described in Example 1 was charged with 1.2 g of aAg-on-SiO₂ fibers catalyst prepared as in Example 1 but containing only1% by weight Ag. The catalyst was reduced by heating for one hour at2500 psi H₂ pressure at 226° C. A 10% by weight solution ofbutanedienepolyperoxide in tetrahydrofuran, containing a known amount of1,6-hexanediol as a standard, was injected and withdrawn at 8 ml/hr withthe reactor temperature at 100° and a hydrogen pressure of 2700-3000psi. After 1.5hrs, the effluent analyzed for a yield of:

47%--1-butene-3,4-diol

25.88%--2-butene-1,4-diol

1.7%--2-hydroxybuten-3-aldehyde and hydroxymethyl vinyl ketone

0.8%--4-hydroxybutyraldehyde

EXAMPLE 3 BEST MODE

A Hastelloy C pressure vessel of 300 ml volume was reduced to a volumeof 115 ml by insertion of a sleeve, which was then packed with 49 g of a10% Ag-on-SiO₂ catalyst prepared as in Example 1 and 245 g of stainlesssteel shot. The reactor was run as a trickle-bed with a diffuser plateat the top to spread the liquid uniformly over the catalyst bed. A sumpat the bottom of the reactor was drained by a dip tube. The injectionand withdrawal rates were matched to keep a constant volume of liquid inthe reactor. A methylacetate solution containing 10% by weightbutadienepolyperoxide and 1.79% by weight of 1,6-hexanediol standard wasinjected and withdrawn at 100 ml/hr at a reactor temperature of 95° C.and a hydrogen pressure of 2300 psi. The effluent contained a yield of

41.15%--1-butene-3,4-diol

26.1%--2-butene-1,4-diol

5.09%--hydroxymethyl vinyl ketone and 2-hydroxybuten-3-aldehyde

4.16%--4-hydroxybutyraldehyde

0.44%--1,4-butanediol

EXAMPLE 4

A solution containing 5% by weight of butadienepolyperoxide plus a knownamount of 1,6-hexanediol as a standard in a 50/50 by weight mixture oftetrahydrofuran and toluene was injected at 180 ml/hr into the apparatusof Example 3 packed with 35 g of 8.35% Ag-on-SiO₂ fibers. The reactortemperature was 95° and the H₂ pressure 2400 psi. The product contained:

54%--1-butene-3,4-diol

26%--2-butene-1,4-diol

<1%--1,2-butanediol

minor amounts--2-hydroxybuten-3-aldehyde hydroxymethyl vinyl ketone4-hydroxybutyraldehyde

EXAMPLE 5

A 300 ml stirred Hastelloy C autoclave was charged with 50 g of a 10%Ag-on-SiO₂ fiber catalyst and a 10% solution of butadienepolyperoxide intetrahydrofuran pumped in at 100 ml/hr at 95° and 2300 psi H₂ pressure.The residence time in the reactor was 55 min. The effluent contained ayield of:

41.06%--1-butene-3,4-diol

22.39%--2-butene-1,4-diol

4.5%--4-hydroxybutyraldehyde

4.29%--hydroxymethyl vinyl ketone and 2-hydroxybuten-3-aldehyde

3.075%--1,2-butanediol

6.30%--1,4-butanediol

15.3%--Unidentified byproducts

EXAMPLE 6

The apparatus of Example 1 was charged with 2.5 g of a 6.14% Ag-on-SiO₂catalyst prepared as in Example 1 but using commercially available, highsurface area silica gel granules as a support. A 10% solution ofbutadienepolyperoxide in tetrahydrofuran, to which 3.26% by weight1,4-hexanediol reference standard had been added, was injected at 95° C.at 2 ml/hr at a H₂ pressure of 2900-3000 psi and withdrawn at the samerate. The product contained:

46.7%--1-butene-3,4-diol

20.4%--2-butene-1,4-diol

1.7%--4-hydroxybutyraldehyde

4.2%--2-hydroxybuten-3-aldehyde and hydroxymethyl vinyl ketone

3.075%--1,2-butanediol

6.30%--1,4-butanediol

15.3%--Unidentified byproducts

EXAMPLE 7

The apparatus of Example 1 was charged with 0.9 g of a 10% Ag-on-SiO₂fiber which had been reduced by washing with an excess of sodiumborohydride in water, then with water until washings were neutral, andfinally tetrahydrofuran. A 10% solution of butadienepolyperoxide intetrahydrofuran, which also contained 1,6-hexanediol as a referencestandard, was injected at 89° C. at 2 ml/hr and 3000 psi H₂ pressure andwithdrawn at the same rate. The product contained:

41.33%--1-butene-3,4-diol

29.38%--2-butene-1,4-diol

10.64%--1,4-butanediol

0.37%--1,2-butanediol

EXAMPLE 8

The reactor of Example 1 was charged with 1.6 g of a 10% Ag-on-coconutcharcoal catalyst and the reduction run at 95° and 2500 psi H₂ injectinga 10% solution of butadienepolyperoxide in tetrahydrofuran plus a1,6-hexanediol standard at 5 ml/hr. After reaching steady-stateconditions, the product contained only traces of saturated diols and wasa mixture of 1-butene-3,4-diol and 2-butene-1,4-diol and unsaturatedaldehydes and ketone.

EXAMPLE 9

2-Butene-1,4-diol was separated by distillation from 1-butene-3,4-dioland other products prepared by the process described in Example 3. Asolution of 0.92779 g 2-butene-1,4-diol with 0.22409 g 1,6-hexanediolstandard in 9 g tetrahydrofuran was prepared. The solution was injectedat 2800 psi and 150° C. at 2 ml/hr into a reactor similar to thatdescribed in Example 1 charged with 1.6 g of a 10% Ag-on-SiO₂ fibercatalyst prepared as in Example 1 and withdrawn at the same rate. Aftera total of 9 ml of the solution was pumped through the system(approximately 4.5 hrs), 0.282 g of 1,4-butanediol was recovered.Essentially all of the 2-butene-1,4-diol had been converted to the1,4-butanediol.

EXAMPLE 10

The apparatus of Example 1 was charged with 6.5 g freshly precipitated,washed and dried silver oxide. The catalyst was reduced by heating at150° C. and 2000 psi H₂ for 2 hrs. The reactor was then cooled to 95° C.and a 10% solution of butadienetetrahydrofuran plus tetraglyme as astandard was injected at 2 ml/hr at 2300 psi H₂ pressure. Whenequilibrium was reached, the product contained a yield of:

47.5%--1-butene-3,4-diol

26.5%--2-butene-1,4-diol

2.8%--4-hydroxybutyraldehyde

0.15%--1,4-butanediol

0.08%--1,2-butanediol

I claim:
 1. A process for hydrogenating butadienepolyperoxide whichcomprises hydrogenating 1-20% by weight of butadienepolyperoxide in asolvent which is stable under the reaction conditions in the presence ofhydrogen and a catalyst consisting essentially of at least 0.1% byweight of metallic silver at a temperature of from 75°-110° C. and apressure of at least 2000 psia to form a reaction product containing1-butene-3,4-diol and 2-butene-1,4-diol the improvement wherein the2-butene-1,4-diol is separated from 1-butene-3,4-diol in the reactionproduct and contacted with hydrogen in the presence of a hydrogenationcatalyst under hydrogenation condition to produce 1,4-butanediol and the1-butene-3,4-diol is contacted with a soluble mercury salt in ahydroxylic solvent at temperatures of 20°-110° C. to produce2,5-dihydrofuran.
 2. A process for hydrogenating butadienepolyperoxidewhich comprises hydrogenating 1-20% by weight of butadienepolyperoxidein a solvent which is stable under the reaction conditions in thepresence of hydrogen and a catalyst consisting essentially of at least0.1% by weight of metallic silver at a temperature of from 75°-110° C.and a pressure of at least 2000 psia to form a reaction productcontaining 1-butene-3,4-diol and 2-butene-1,4-diol the improvementwherein the 2-butene-1,4-diol is separated from 1-butene-3,4-diol in thereaction product and the 1-butene-3,4-diol is contacted with a solublemercury salt in a hydroxylic solvent at temperatures of 20°-110° C. toproduce 2,5-dihydrofuran.